Fluid treatment of rectangularly piled polyacrylonitrile tow



Sept. 19, 1961 IN V EN TORS.

ARTHUR CRESSWELL, PERG/VAL W CUMMINGS Jr. RODNEY 7.' SWAIN WWI- A A TTOR/VEY.

U t d S s Patent ,0 ,6 FLUID TREATMENT OF RECTANGULARLY FILED POLYA'CRYLONITRILE TOW Arthur Cresswell, Stamford, Percival W. Cummings, Jr., Cos Cob, and Rodney T. Swain, Darien, (Jonnn, as-

signors to American Cyanamid Company, New York, N.Y., a corporation of Maine Filed Oct. 5, 1955, Ser. No. 538,618 Claims. (Cl. 8-152) This invention relates broadly to a method of treating tow, especially tow formed of synthetic filamentary material; and, more particularly, is concerned with a method of continuously removing residual shrinkage from a tow of continuous filaments comprised of a polymer (fiberforming polymer) of acrylonitrile and which is capable of being further shrunk. It was known prior to our invention that continuous filaments comprised of a polymer of acrylonitrile, when dried, will shrink when placed in boiling water (see, for instance Cresswell and Wizon US. Patent No. 2,558,733 date July 3, 1951, column 4, lines 53-63).

' It is a primary object of the present invention to provide a new and improved method of continuously removing residual shrinkage from a tow of continuous filaments comprised of a polymer of acrylonitrile and which is capable of undergoing further shrinkage.

. It is a further object of our invention to provide such a process as aforementioned using relatively inexpensive apparatus, at a relatively low operating cost and with minimum attention from an operator.

It is another object of the instant invention to provide a continuous process of removing residual shrinkage fiom a tow of the kind with which this invention is concerned and which can be synchronized with other continuous steps of the over-all process, including the steps of drying and of crimping, the former step normally preceding and the latter step normally following the hereindescribed treatment to remove residual shrinkage.

Other objects of the invention will be apparent to those skilled in the art from the following more detailed description and the accompanying drawing which is illustrative of the invention and wherein:

FIG. 1 is a perspective view showing, schematically, apparatus adapted for use in practicing a preferred embodiment of the invention;

FIG. 2 is an enlarged perspective view of portions of the apparatus shown in FIG. 1; and

FIG. 3 is a plan view of a portion of the apparatus shown in FIGS. 1 and 2 and illustrating the manner in which the tow is deposited therein.

In the production of a polyacrylonitrile fiber, that is, a fiber of homopolymeric or copolymeric acrylonitrile, it is desirable in most cases from a commercial standpoint (an exception being when so-called bulk yarns are to be produced and wherein the residual shrinkage is desirable) that the residual shrinkage normally present in the fiber after a drying operation be removed completely or almost completely therefrom so that the spun yarn, and especially fabrics woven or knitted from such yarn, Will have either no shrinkage whatsoever or minimum shrinkage during hot operations to which the fabric may be subjected, e.g., dyeing, drying, laundering, etc. In the case of continuous-filament yarn, the residual shrinkage conveniently may be removed by continuously passing the yarn in a relaxed stated through a so-called relaxation furnace or zone as is described more fully in, for example, Cresswell and Wizon US. Patent No. 2,558,733, dated July 3, 1951. However, to the best of our knowledge and belief, no completely satisfactory continuous method was known prior to our invention for continuous- 1y removing residual shrinkage from a tow of continuous synthetic filaments, and more particularly filaments comprised of a polymer of acrylonitrile.

The objects of the invention are attained by the method of the present invention. Briefly described, the method comprises continuously passing a tow of the kind with which this invention is concerned, in a relaxed or freeto-shrink state, through a zone comprised of liquid, e.g.,. Water or other liquid alone or water or other liquid admixed or in contact with a hot gaseous medium, e.g., steam. The temperature of this zone is within the range of from about 99 C. to about 110 C., and whenthe zone is composed of water the temperature is generally of the order of from about 99 C. to 100 C. The hot treating-liquid is introduced into the treating zone either continuously or intermittently, as desired or as condi-ftions may require. For example, the liquid may be in-' troduced alternately first from one side of the zone, e.g.,, at or near the inlet end to the zone, and then from the opposite side. A portion of the tow to be treated is maintained in the treating zone in contact with the hot liquid for a period sufficient to reduce the residual shrinkage to from 0% to not more than about 2% or 3% To effect this result the contact period is usually at least 5 seconds, e.g., from 5 seconds to 30 minutes or longer. The tow is retained in the treating zone for the required residence time while continuously introducing untreated tow into the inlet end of the treating zone and continuously withdrawing treated tow from the outlet end of said zone.

Referring to the drawing there is shown schematically in FIG. 1 apparatus by the use of which the method of the invention can be carried into effect. The tow10 of continuous, oriented filaments comprised of a polymer of acrylonitrile and containing residual shrinkage advantageously is first wetted with water by suitable means in order to facilitate subsequent handling, although it is not necessary that this be done. The tow that is processed in practicing the present invention may be one that has been produced either by a dry-spinning or by a wet-spinning method. In the latter case the oriented, gelled tow is commonly first dried in a suitable dryer, and then treated as herein described to remove residual shrinkage.

One suitable means of wetting the dried tow with water is the wetting device 12. Before entering this device the tow usually passes through the tow guide 14 and, after leaving the wetting device, passes through the tow guide 16 a The wetting device, if employed, may be of any suitable form, e.g., a spray, trough, tu-be, wiper, etc. As shown in FIG. 1 for purpose of illustration, the wetting device 12 is comprised of an outer tube 18 and an inner tube 20. The latter is provided with a plurality of openings or orifices along an upper section or sections thereof so that water entering the device through the inlet conduit 22 and thence flowing through the passageway 24 formed between the outer and inner tubes can pass through the aforementioned openings onto the tow 10 passing through the wetting device. The excess water is drained from the device through the drains 26 and 28, which latter carries away the water that falls into the drain pan 30 attached to the discharge end of the said Wetting device.

From the wetting device 12 the wetted tow moves continuously to a treating zone for removing residual shrinkage as herein described. Such a zone advantageously is provided by means of the J-box 32, the tow passing en route thereto through the traverse mechanism 34 and thence over the rolls 36, 38 and 40. A drip pan 42 having a drain 44 advantageously may be provided for collecting and removing any water that drips off the tow mechanism 34.

Traverse mechanism 34, as shown in FIG. 2, is comprised of a metal block 110 which is rigidly fastened to traversing rod 114 and which is guided smoothly in its reciprocating motion by stationary guide rod 112. The reciprocating motion of the traverse mechanism 34 is provided by a roller cam follower and cam (not shown) of suitable stroke. The smooth motion of the traverse mechanism is made possible by the use of ball bearing bushings (not shown), one of which is clamped inside block 110 around guide rod 112 and the others clamped to a framework (not shown) to provide support for traversing rod 114.

Metal block 110 is provided on its lower end with a bracket 116 which holds the tow guide 118 in a suitable position relative to tow guide 16, drip pan 42 and roll 36. Metal block 110 is provided on its upper end with a yoke 80, having arms 78 and 88, rigidly attached. Ann 78 and 88 necessarily include some adjusting means (not shown) for actuating the switch lever 82 at the desired point in the cycle for the purpose of controlling the configuration of the deposit of tow.

' The fluted, lower roll 36 and the upper roll 38 revolve in opposite directions and the tow passes over them as is shown in FIG. 1. The upper roll 38 is provided with a pinch roll 46, the weight of which is such that the tow is pinched against the surface of the roll 38. The pinch roll thus provides traction so that the tow is under tension at least suflicient to move it to the point of contact of the pinch roll 46 upon the surface of the roll 38, and is under little or no tension after it leaves that point. From the roll 38 the tow passes over the fluted, feed roll 40 and thence falls downwardly in a relaxed, free-to-shrink condition into the inlet end 48 of the J-box 32.

' The upper roll 38 revolves at a peripheral speed which is the same as or slightly higher than that of the peripheral speed of the lower roll 36; while the feed roll 40 revolves at a peripheral speed which is the same as or slightly higher than that of the peripheral speed of the upper roll 38. Downward fall of the tow from the feed rbll 40 is facilitated by its wetted condition and the resulting weight of the falling portion.

I The J-box 32, having a front wall 50 and a back wall 51,is provided at its inlet end 48 with spray means 52 on one side thereof and spray means 54 on the opposite side. The spray means are comprised of a spray header 56 and openings 58 in the side wall 61 for spray means 52, and spray header 60 and openings 62 in the side wall 63 for spray means 54. In FIG. 2 the upper wall of the spray header 56 is shown broken away so that the openings 58 will be visible.

In operation, the cycle may be described with the tow entering the J-box at, for example, the corner 64 (FIG, 3 and when (disregarding the time lag) the traverse ntie chanism 34 is travelling from front to back, thereby causing the tow to travel towards the back wall 51 of the inlet end of the J-box. With the water-spray system in use and electrical current being supplied through the power line 65 on the valve-control circuit of the apparatus the action is as follows:

Switch 66 (FIG. 2), e.g., a maintained contact limit switch, single pole, double throw, is in such a position that valve 68, through which water or other liquid is introduced to the spray means 52 through the conduit 70, is held open by the current, and valve 72 through which water can be introduced into the spray means 54 through the conduit 74 is closed, receiving no electrical current. Valves 68 and 72 may be, for example, normally closed sglenoid-operated water valves. Water or other liquid at the desired elevated temperature flows through the conduit 76 from a supply source (not shown) and thence through valve 68 to the spray means 52. The tow reaches the corner 64 due to the fact that the liquid spraying through the holes 58 in the side wall 61 of the upper portion of the J-box 32 forces the downwardly moving tow enter the J-box at the inlet end 48 toward that corner.

When the traverse mechanism 34 reaches the back end of its stroke, the arm 78 of the yoke 80 forces the switchactuating lever 82 into its alternate position. This causes the switch 66 to open the circuit to valve 68 and close the circuit to valve 72 Valve 68 then closes and shuts off the liquid to spray means 52, and valve 72 opens and supplies liquid tospray means 54 on the opposite side of the upper portion of the J-box.

While, the actions described in the preceding paragraph are taking place the tow is approaching the corner 84 (FIG. 3) of the J-box. When the supply of liquid is applied to the tow by the spray means 54 the tow is forced to the opposite side of the box toward the corner 86. It is held toward the side 61 of the box by the spray of liquid until the traverse mechanism 34 completes its stroke. When the traverse mechanism reaches the front end of its stroke, and the tow is approaching the corner 87, the arm 88 of the yoke 80 forces the switch-actuating lever 82 into its original position, causing the switch 66 to close the circuit to valve 68 and open the circuit to valve 72. Valve 68 is thus opened and valve 72 is closed. The liquid entering the spray means 52 and thence through the openings 58 forces the tow over toward corner 64 and the operation repeats.

The action of the alternate application of a spray of liquid first from one side of the inlet end of the J-box and then from the opposite side causes the tow to be deposited in the treating zone in the desired configuration, for instance, as shown at 90 in FIG. 3. In the absence of suitable means, e.g., alternating spraying means such as that herein described, the tow piles up or tends to pile up in a narrow pile directly under the discharge side of the feed roll 40, finally toppling over and causing tangling on the discharge side of the J-box.

The plaited tpw is carried downwardly tothe middle portionf92 of the J-box which is jacketed. A hot fluid medium, for example, water at 99 C. to 6., steam or other hot fluid of the desired temperature, is introduced through the gonduit 94 into the jacket and withdrawn through the conduit 96. The water or other liquid introduced into the upper portion of the J-box through the spray means 52 and 54 occupies the space, along with the tow, in the middle portion of the J-box. The conduit 98 permits the draining of excess water from leg 108 of the J-box to the receptacle 104. Openings 100 in the leg 102, where indicated, permit the water which has flowed with the and through the mass of tow to escape into the receptacle 104 from which it then flows through the conduit 106.

inlet conduit 94 provides means for introducing a hot fluid medium, e.g., hot water, steam, oil, etc., to the jacket surrounding the middle portion 92 of the J-box; while outlet conduit 96 provides means for withdrawing the said hot fluid medium. Circulation of this hot fluid medium through the said jacket maintains the temperature of the liquid and tow in the middle portion 92 at the desired point.

In operation, a head of liquid normally builds up in the leg 108 of the J-box, and this liquid head assists in carrying the deposited tow through the middle portion of the J-box. The rniddle portion of the J-box through which the tow passes is so constructed that there are no sharp corners and hence there are no obstructions to thg free movement of the tow through this portion of the box. The tow is retained in contact with the hot liquid in the bottom portion of the J-box 32 for the desired period and which may range from 5 seconds to 30 minutes or more. While the tow is retained in this bottom portion of the J-box, untreated tow is being continuously introduced into the inlet end 48 of the J-box as above described and treated tow is continuously being withdrawn from the outlet end of the J-bpn at such a rate that the amount of retained tow within the J-box remains substantially constant.

In the foregoing description reference has been made specifically to the use of water at a temperature of from abount 99 C. to 100 C. as the liquid that is introduced into the treating zone, e.g., a J-box. As alternative liquids in place of Water for shrinking the tow in the treating zone may be used such non-solvent liquids (that is, liquids which do not dissolve or harmfully afiect the tow) as ethylene glycol, diethylene glycol, ethylene glycol monoethyl ether, glycerol, propylene glycol and the like. It is desirable that such alternative treating liquids, if employed (either alone or with water or other liquid), be miscible with water so that they may be readily and economically removed subsequent to the shrinking treatment by washing the tow with water. The use of liquids of the type described above permits the shrinking operation to be carried out at temperatures above 100 C., say 110 C., at atmospheric pressure without distillation of the liquid.

Instead of the particular means described hereinbefore, and illustrated in the accompanying drawing, for actuating the traverse mechanism 34, various other means can be used; for example, one could use a straight-line, reciprocating electric motor, or an air cylinder or a hydraulic cylinder provided with adjustable valves for alternating the direction of stroke automatically.

Likewise, instead of the particular means hereinbefore described for actuating the valves 68 and 72 various other means can be used. For instance, the switch 66 could be replaced with an air valve and the solenoid coils of the valve 68 and 72, with diaphragm-type or cylinder-type valve operators; or the valves 68 and 72 could be mechanically actuated by cams attached to the drive mechanism of the traverse, or directly by the action of the reciprocating ends of the traversing rod.

It has been mentioned hereinbefore that the tow used in practicing the present invention may be one produced either by a dry-spinning or by a wet-spinning method; and that in the latter case the oriented, gelled tow is commonly first dried in a suitable dryer. Such drying means may take the form of, for example, an apron dryer or the obvious equivalent thereof and whereby the tow is dried in a gaseous atmosphere, for instance an atmosphere of air. Tow produced by a dry-spinning process may be processed as herein described, for example, after the freshly spun tow has been washed to remove residual solvent, oriented by stretching and the wet material then dried, if necessary, in a gaseous atmosphere.

The following more specific examples are further illustrative of our invention and of the results obtained by practicing it. All parts and percentages are by weight.

Example 1 A ternary polymer of about 87.6% acrylonitrile, 6 .0% vinyl acetate and 6.4% 2-methyl-5-vinylpyridine is dissolved in 46% aqueous sodium thiocyanate to make a viscous solution containing by weight of ternary polymer. After deaerating and filtering, this solution is extruded through several multi-hole spinnerettes having 90 micron diameter holes into a coagulating bath comprising 10% aqueous sodium thiocyanate which is circulating and maintained at -2 C. The gel multi-filament tow, which forms on coagulation in this bath, is countercurrently washed with water until substantially free of sodium thiocyanate, after which it is immediately stretched 9-fold to yield an oriented gel multi-filament tow of 2.18 denier per filament on the dry denier basis.

The gel tow is fed without tension into an apron dryer. The residence time of the tow in the dryer is 20 minutes; during this tensionless gel drying the tow shrinks 12.3% and the filament denier increases to 2.48. The thusly dried tow still contains residual shrinkage; that is, it is capable of undergoing further shrinkage.

The dry-tow is then rewetted with water and fed without tension into a J-box in which the tow is plaited by alter nating jets of water at 99 C. as hereinbefore described. The J-box is well insulated to retain the temperature of the hot water. The tow is allowed to accumulate in the J-box for 26 minutes, at which time the treated tow is withdrawn from the discharge side of the J-box at the same rate in weight per unit time that it is fed in. During this treatment with hot water the dry tow undergoes a further shrinkage amounting to 14.9% of the dry tow length and the filament denier increases to 2.93 on the dry basis. This treated tow shrinks only about 2% when placed in rapidly boiling water.

Example 2 Gel tow which has been prepared as described in the first paragraph of Example 1 is washed with 1% aqueous H prior to its first drying as tow. The tow is then dried under no tension in an apron dryer. After delivery from the dryer the tow has a filament denier of 2.6; the residual shrinkage in boiling water is 12.8%.

The dry tow is rewetted with water and fed without tension into a J-box containing circulating 1% aqueous H 80 maintained at 100 C.; the residence time in the J- box before withdrawing is 26 minutes. During this treatment the tow undergoes a shrinkage of 21.2% of the dry tow length and the filament denier becomes 3.3 on the dry basis. This treated tow does not shrink when placed in rapidly boiling water.

Example 3 Tow spun, washed, stretched and dried as in Example 1 is rewetted and fed without tension into a heated J-box in which a solution of 50% ethylene glycol and 50% water is circulated at 107 C. The tow undergoes a further shrinkage of 20% by this treatment, the denier increasing to 3.1. After washing with water and redrying this tow does not shrink when placed in rapidly boiling water. 7

Example 4 Tow spun, washed, stretched and dried as in Example 1 is rewetted with water and fed without tension into a heated J-box in which the tow is plaited by alternating jets of water at 100 C. as hereinbefore described. The temperature of the water within the J-box is maintained at 100 C. and the tow, by continuously feeding in and withdrawing at equivalent weight rates, is maintained within the heated zone for 21 minutes. After this treatment the tow is found to have shrunk 15.2% of the length as fed into the heated zone and the denier increases to 3.035. The treated tow does not shrink when placed in rapidly boiling water.

Example 5 Example 1 is repeated with the exception that, instead of using a tow of continuous filaments comprised of the described ternary polymer of acrylonitrile, vinyl acetate and 2-methyl-5-vinylpyridine there is employed, in one test (a), a similarly prepared tow of continuous filaments composed of homopolymeric acrylonitrile (average mo lecular weight, about 75,000); and in another test (b), a similarly prepared tow of continuous filaments comprised of a copolymer of about acrylonitrile and 5% methyl acrylate (average molecular weight, about 78,000). Substantially the same results are obtained as in Example 1, the treated tows shrinking only from about Vz% to about 2% when placed in boiling water.

It will be understood, of course, that our invention is not limited to the specific means shown in the accompanying drawing for carrying the present invention into effect; and certain modifications of the means that can be employed were mentioned in a portion of this specification prior to the examples. Similarly, our invention is not limited to the processing of tows of continuous filaments comprised of the particular polymers of acrylonitrile employed by way of illustration {in the foregoing examples. To the best of our knowledge and belief the present invention is operative with any tow of continuous filaments comprised of a polymer .of acrylonitrile. Such polymers include fiber forming (fiber-formable) homopolymeric acrylonitrile and fiber-forming (fiber-,formable) acrylonitrile copolymers (thermoplastic acrylonitrile co polymers) containing in the polymer molecules an average of at least about 40% preferably at least about 75% by weight of combined acrylonitrile. Tows of continuous filaments comprised of such polymers can be employed in carrying the present invention into effect. I

Acrylonitrile polymerization products of the kind aforementioned are prepared by methods now well known to those skilled in the art. In some cases the polymerization rates of the individual monomers in a polymerizable mixture may be diiferent, with the result that the proportions of the components in the final copolymer are different from the proportions thereof in the mixture of monomers which is polymerized. The proportions of monomers in the polymerizable mixture therefore preferably are adjusted so that the final copolymer contains in the molecules thereof an average of at least about 40%, preferably at least about 75%, by weight of combined acrylonitrile. The expression an acrylonitrile polymer containing in the polymer molecules an average of at least 75% by weight of combined acrylonitrile, as used herein and in one of the appended claims, means a polymerization product (homopolymer, copolymer or graft polymer or mixtures thereof) containing in the molecules thereof an average of at least 75% by weight of the acrylonitrile unit, which is considered to be present in the individual polymer molecules as the group or, otherwise stated, at least 75% by weight of thereactant substance converted into and forming the polymerization product is acrylonitrile.

Illustrative examples of monomers which maybe copolymerized with acrylonitrile to yield a polymerization product containing in the polymer molecules an average of at least about 40%, preferably at least about 75%, by weight of combined acrylonitrile are compounds containing a single CH =C grouping, for instance, the vinyl esters and especially the vinyl esters of saturated aliphatic monoca-rboxylic acids, e.g., vinyl acetate, vinyl propionate, vinyl butyrate, etc.; vinyl and vinylidene halides, e.g., the vinyl and vinylidene chlorides, bromides and fluorides; allyl-type alcohols, e.g., allyl alcohol, methallyl alcohol, ethallyl alcohol, etc.; allyl, methallyl and other unsaturated monohydric alcohol esters of monobasic acids, e.g., alkyl and methallyl acetates, laurates, cyanides, etc.; acrylic and alkacrylic acids (e.g., methacrylic, ethacrylic, etc.) and esters and amides of such acids (e.g., methyl, ethyl, propyl, butyl, etc., 'acrylates and methacrylates, acrylamide, :methacrylamide', N- met-hyl, -ethyl, -propyl, -butyl, etc., acrylamides and methacrylamides, etc); methacrylonitrile, ethacryl on'itrile and other hydrocarbon-substituted acrylonitrilesj unsaturated aliphatic hydrocarbons containing 1 a single CH =C grouping, e.g., isobutylene, etc.;and numerous other vinyl, acrylic and other compounds containing a single CH ==C grouping which are copolymerizable with acrylonitrile to yield thermoplastic copolymers. Alkyl esters of alpha, beta-unsaturated polycarboxylic acids also may be copolymerized with acrylonitrile to form copolymers which are useful in practicing the present invention, e.g., the dimethyl, -ethyl, '-propyl, ebutyl, etc., cs'tersof maleic, fumaric, citraconic, etc.,.acids;

Ordinarily the molecular weight (average molecular weight) of the acrylonitrile polymerization product (polymer of acrylonitrile) used in makingthetow offcon'tinuone filaments preferably employed in practicing Your in+ vention is within the range of 25,000 or 30,000 to 200,000 or 300,000 or higher, and advantageously is of the order of 50,000 to 100,000, e.g., about 70,00080,000, as calculated from a viscosity measurement of the said polymerization product in dimethyl formamide using the Standinger equation (reference: US. Patent No. 2,404,713).

It also will be understod by those skilled in the art that the tow of continuous filaments can be produced by spinning a solution'of a mixture or blend of different polymers including a polymer (homopolymer or copolymer) of acrylonitrile. For instance, the spinning solution may contain a mixture of a homopolymer of Z-methyl-S-vinylpyridine and a copolymer of about -95% by weight of acrylonitrile and about 5-10% by weight of acrylic acid, acrylamide, vinyl acetate, methyl acrylate, etc., the aforesaid homopolymer constituting from about 5% to 10% of the total polymers present in the spinning solution; or, instead of the homopolymer of Z-methyl-S-vinylpyridine, one could use a copolymer of, for instance, 15% to 50% of a vinylpyridine, e.g. Z-methyl-S-vinylpyridine, and the remainder acrylonitrile.

All the tows of continuous filaments used in carrying our invention into etfect contain residual shrinkage, that is, they are capable of undergoing further shrinkage; and while we have described our invention with particular reference to the removal of residual shrinkage from a tow of continuous filaments comprised of a polymer of acrylonitrile, it is mentioned that this has been done mainly for purpose of illustration. Consequently, we do not wish to preclude the processing, in accordance with our invention, of a tow of continuous synthetic filaments comprised of other fiber-forming materials either alone or in combination with a polymer of acrylonitrile; or tows composed of a plurality of different kinds of continuous synthetic filaments, e.g., continuous filaments composed of a polymer of acrylonitrile and one or more different continuous filaments comprised or composed of a diiierent synthetic material or materials.

We claim:

1. The method of continuously removing residual shrinkage from a tow of continuous filaments consisting essentially of a thermoplastic polymer of acrylonitrile and said filaments being capable of being further shrunk, said method comprising continuously introducing said tow, in a relaxed state, downwardly into the inlet end of a treating zone in the form of a J-box; causing a traverse motion to be applied to said tow as it enters said inlet end of said zone; depositing the tow in a four-sided pattern in which opposite sides are approximately parallel to each other by applying a spray of an inert liquid to the side of said downwardly, traversely moving tow at frequent, regular intervals as the tow approaches the limit of its traverse motion, said spray being applied first from one side of said inlet end and then from the opposite side, and said inert liquid from said spray being at a temperature of from about 99 C. to about 110 C. and being collected in a bottom portion of said treating zone where it is maintained at said temperature; and maintaining a portion of said tow in said zone for a period of at least 5 seconds while continuously introducing untreated tow as above described into the inlet end of said-treating zone and continuously withdrawing treated tow from the outlet end of said zone.

2. A method as in claim 1 wherein the inert liquid is water at a temperature of from about 99 C.,to 100 C.

3. The method of continuously removing residual shrinkage from a tow of wet-spun, continuous filaments consisting essentially of a thermoplastic polymer of acrylonitrile and said filaments being capable of being further shrunk, said method comprising continuously introducing said tow, after being dried in a gaseous atmospheredownwardly into the inlet end of a treating zone in the form of a J-box, said tow being in a relaxed state while it is in said zone; causing a traverse motion to be applied to said tow as it enters said inlet end of said zone; depositing the tow in a four-sided pattern in which opposite sides are approximately parallel to each other by applying a spray of water to the side of said downwardly, traversely moving tow at frequent, regular intervals as the tow approaches the limit of its traverse motion, said spray being applied first from one side of said inlet end and then from the opposite side, and said water from said spray being at a temperature of from about 99 C. to 100 C. and being collected in a bottom portion of said treating zone where it is maintained at said temperature; and retaining the continuously moving tow in contact with said water in the said bottom portion of said treating zone for a period of at least seconds while continuously introducing untreated tow as above described into the inlet end of said treating zone and continuously Withdrawing treated tow from the outlet end of said zone.

4. A method as in claim 3 wherein the tow, after being dried in a gaseous atmosphere, is wetted with water prior to passage through the said zone of water at a temperature of from about 99 C. to 100 C.

5. The method of continuously removing residual shrinkage from a tow of continuous filaments consisting essentially of a thermoplastic acrylonitrile polymer containing in the polymer molecules an average of at least 75% by weight of combined acrylonitrile and said filaments being capable of being further shrunk, said method comprising continuously introducing said tow, in a relaxed state, downwardly into the inlet end of a treating zone in the form of a J-box; causing a traverse motion to be applied to said tow as it enters said inlet end of said zone; depositing the tow in a four-sided pattern in which opposite sides are approximately parallel to each other by applying a spray of water to the side of said downwardly, traversely moving tow at frequent, regular intervals as the tow approaches the limit of its traverse motion, said spray being applied first from one side of said inlet end and then from the opposite side, and said water from said spray being at a temperature of from about 99 C. to 100 C. and being collected in a bottom portion of said treating zone where it is maintained at said temperature; and retaining the continuously moving row in contact with said water in the said bottom portion of said treating zone for a period of from 5 seconds to 30 minutes while continuously introducing untreated tow as above described into the inlet end of said treating zone and continuously withdrawing treated tow upwardly from the outlet end of said zone.

References Cited in the file of this patent UNITED STATES PATENTS 2,334,066 Campbell Nov. 9, 1943 2,445,042 Silverman July 13, 1948 2,663,177 Hanhart Dec. 22, 1953 2,712,977 Keggin July 12, 1955 2,721,371 Hodkinson et al. Oct. 25, 1955 2,725,277 Rilling Nov. 29, 1955 OTHER REFERENCES Papers of the Amer. Association of Textile Technologists for March 1949, pp. and 66.

UNITED STATES PATENT OFFICE CERTIFICATE 0E CORRECTION A Patent No. 3,000,691 v September 19, 1961 Arthur Cresswell et al,

I It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as "corrected below Column 3, line 17, for "Arm" read Arms column 3*, line 1, for "enter" read entering line 4:9, strike out "the", first occurrence; column 7, line 34, for "molecules" read molecule line 54, for "'alkyl" read allyl column 8, line 7, for "understod" read understood Signed and sealed this 3rd day of April 1962.

(SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents 

1. THE METHOD OF CONTINUOUSLY REMOVING RESIDUAL SHRINKAGE FROM A TOW OF CONTINUOUS FILAMENTS CONSISTING ESSENTIALLY OF A THERMOPLASTIC POLYMER OF ACRYLONITRILE AND SAID FILAMENTS BEING CAPABLE OF BEING FURTHER SHRUNK, SAID METHOD COMPRISING CONTINUOUSLY INTRODUCING SAID TOW, IN A RELAXED STATE, DOWNWARDLY INTO THE INLET END OF A TREATING ZONE IN THE FORM OF A J-BOX; CAUSING A TRAVERSE MOTION TO BE APPLIED TO SAID TOW AS IT ENTER SAID INLET END OF SAID ZONE; DEPOSITING THE TOW IN A FOUR-SIDED PATTERN IN WHICH OPPOSITE SIDES ARE APPROXIMATELY PARALLEL TO EACH OTHER BY APPLYING A SPRAY OF AN INERT LIQUID TO THE SIDE OF SAID DOWNWARDLY, TRAVERSELY MOVING TOW AT FREQUENT, REGULAR INTERVALS AS THE TOW APPROACHES THE LIMIT OF ITS TRAVERSE MOTION, SAID SPRAY BEING APPLIED FIRST FROM ONE SIDE OF SAID INLET END AND THEN FROM THE OPPOSITE SIDE, AND SAID INERT LIQUID FROM THE SPRAY BEING AT A TEMPERATURE OF FROM ABOUT 99*C. TO ABOUT 110*C. AND BEING COLLECTED IN A BOTTOM PORTION OF SAID TREATING ZONE WHERE IT IS MAINTAINED AT SAID TEMPERATURE, AND MAINTAINING A PORTION OF SAID TOW IN SAID ZONE FOR A PERIOD OF AT LEAST 5 SECONDS WHILE CONTINUOUSLY INTRODUCING UNTREATED TOW AS ABOVE DESCRIBED INTO THE INLET END OF SAID TREATING ZONE AND CONTINUOUSLY WITHDRAWING TREATED TOW FROM THE OUTLET END OF SAID ZONE. 